English lavenders are great. Can get small plants grown from cuttings from independent garden centres often in spring. Drought tolerant, loved by bees.
Drumstick alliums (Allium sphaerocephalon) are great for bees and look after themselves. Perennial. Look best in clumps next to lower growing plants.
Hoverflies like "umbel" flowers, so achilleas / yarrows, things like dill or fennel. I sow 'Dutch mammoth' dill alongside cornflowers as they're a similar height.